1. Field of the Invention
This invention provides record material comprising paper sheets coated with isolated liquid droplets which include 2,2,4 -trimethyl-1,3 -pentanediol diisobutyrate. Said isolated liquid droplets are associated, on the record material, with at least two color-producing reactants, at least one of which is soluble in said liquid. The liquid is associated with the reactants either by being in close proximity to both reactants or by having one of the reactants dissolved therein and being in close proximity to the other. Of the color-producing reactants, one is a chromogenic dye-precursor and one is a coreactant material capable of developing the color of the chromogenic dye-precursor when the two reactants are brought into reactive contact by rupture of the isolating medium. Isolation of the liquid droplets is preferably accomplished by encapsulation of the droplets with pressure-rupturable, solid, polymeric, film material.
2. Description of the Prior Art
In the art of making pressure-sensitive record material, of the type described, which includes liquid-containing-microcapsules, successful commerical embodiments have made use of Crystal Violet Lactone (hereinafter called CVL) as chromogenic dye-precursor material, and acidic coreactant material such as attapulgite clay or an oil-soluble, para-substituted-phenol-aldehyde novolak resin, and a liquid solvent that is at least in part isopropyl-biphenyl as disclosed in U.S. Pat. No. 3,627,581, issued Dec. 14, 1971 on the application of P. S. Phillips, Jr. Isopropyl-biphenyl has a low vapor pressure and good solvent power and is readily retained by gelatin films (a widely used capsular wall material). Isopropyl-biphenyl has, therefore, served well as a solvent in pressure-sensitive record material systems of the type disclosed. U.S. patent application Ser. No. 522,001, filed Nov. 8, 1974, in the name of Erland C. Porter, Jr., which is a continuation of
U.S. patent application Ser. No. 326,361, filed Jan. 24, 1973 now abandoned, discloses that ethyldiphenylmethane provides print intensity and fade resistance improved over isopropyl-biphenyl when used with a dye system including CVL and with standard commercial receiving sheets sensitized, for example, according to the teaching of U.S. Pat. No. 3,663,256, issued May 16, 1972 on the application of R. E. Miller and B. W. Brockett.